#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int ch = 0;
	while ((ch = getchar())!= EOF)
	{
		if ((ch >= 'a'&&ch <= 'z')||(ch >= 'A'&&ch <= 'Z'))
		{
			printf("YES\n");
		}
		else
		{ 
			printf("NO\n");
		}
		getchar();
	}
	return 0;
}